Regarding the trends in Collin, Denton, Galveston, Brazoria, and Bell that some people asked about here are the net results for 2012, 2016 and 2018 showing the trend.
Collin 2012-95,473, 2016-60,390, 2018-21,811
Denton 2012-76,601, 2016-59,713, 2018-24,095
Galveston 2012-29548, 2016-30,099,2018-22,576
Brazoria 2012-36,441, 2016-29,591, 2018-20,465
Bell 2012-14,062, 2016-14,187, 2018-9,020
There is also the fact that the generic ballot was plus 7 or 8 before Biden's polling average shot up over 10. And another fact that both Clinton and Beto beat their polling average in Texas by around 3% indicting that pollsters are not accounting for the true percentage of Democratic voters. I think the polling could be off by as much as 4-5% this time.
I thinking Biden wins Collin and Denton by less than 10K, while Trump wins Galveston and Brazoria, by around 10K, with Bell a tossup that could go a couple thousand votes either way.
The early voting in 2016 and 2018 favored the Democrats in Texas, so I see early voting success as a good sign, not something to worry about.
Montgomery is still not close. The trend is Montgomery 2012-105,409, 2016-104,479, 2018-86,127. So Trump should win it by 50-70K. But if Democrats net 20K when compared to Beto's result that is still a nice plus as it all adds up.